Radial Velocity Search for Extrasolar Planets in Visual Binary Systems

• Published in: Publications of the Astronomical Society of Japan Vol. 61; no. 1; pp. 19 - 28
• Main Authors: Toyota, Eri, Itoh, Yoichi, Ishiguma, Shinichiro, Urakawa, Seitaro, Murata, Daisuke, Oasa, Yumiko, Matsuyama, Hiroko, Funayama, Hitoshi, Sato, Bun’ei, Mukai, Tadashi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford University Press 25.02.2009
• Subjects: techniques: radial velocities; binaries: visual; planetary systems
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/61.1.19

We searched for extrasolar planets in visual binary systems using precise Doppler-shift measurements taken over a period of 4 yr. Using the HIgh Dispersion Echelle Spectrograph (HIDES) equipped on the Okayama Astrophysical Observatory (OAO) 188 cm reflector, we achieved a radial-velocity precision of about 10 ms $^{-1}$ . We monitored both primary and secondary stars of six visual binary systems, and primary stars of three visual binaries. Among them, three objects show large radial-velocity variations. ADS 7311 A exhibits a decreasing trend in radial velocity with a best-fit slope of $-$ 30 ms $^{-1}$ yr $^{-1}$ , while 31 Dra A shows an increasing trend with a best-fit slope of $+$ 220 ms $^{-1}$ yr $^{-1}$ . These long-term trends in radial velocity may be attributable to unseen companions. BDS 10966 A shows a periodic variation in radial velocity with a period of 840 d and a semiamplitude of about 120 ms $^{-1}$ , implying an association of a planetary-mass companion, rotational modulation, or nonradial oscillation of the photosphere. In any case, we should mention the nonassociation between BDS 10966 A and B, suggested by the different proper motions, radial velocities, and Hipparcos parallaxes.